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A civil defense siren is a siren used to provide an emergency population warning to the general population of approaching danger. Initially designed to warn city dwellers of air raids ( air-raid sirens ) during World War II , they were later used to warn of nuclear attack and natural disasters , such as tornadoes ( tornado sirens ).
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In a pneumatic siren, the stator is the part which cuts off and reopens air as rotating blades of a chopper move past the port holes of the stator, generating sound. The pitch of the siren's sound is a function of the speed of the rotor and the number of holes in the stator. A siren with only one row of ports is called a single tone siren.
A fire truck running the E-Q2B siren. Today Federal Signal's Q2B siren is still in wide use. The majority of users of the Q Siren are fire departments, although some ambulances and heavy rescue squads have employed the Q-siren. The Q-siren produces 123 decibels at 10 feet (3.0 m) with an operating current of 100 amps at 12 V DC (1.2 kW). [1]
A Federal Signal Thunderbolt 1003 siren. The Thunderbolt is a mechanical outdoor warning siren that was manufactured by Federal Signal Corporation from 1951 until its production ended in 1991. [1] It is a unidirectional, rotating siren with a large square-shaped horn, and can come in various colors, usually yellow, by request.
(The Center Square) – Wisconsin Gov. Tony Evers said he intends to propose spending $80 million on farms, farm families, processors and producers in his upcoming biennial budget proposal ...
A siren disk is used in pneumatic sirens and has holes which are variously spaced apart. When the disk is spun in front of a jet of air, the holes modulate the air-jet which produces a sound. The pitch of a siren is produced by "the frequency of the impulses of compressed air passing through the openings in a rotating disk."
The siren suit is a one-piece garment for the whole body which can easily be put on or taken off, originally designed for use on the way to, and in, air-raid shelters. [1] The suit solved the problems of warmth and modesty encountered when seeking shelter during nighttime air raids in the United Kingdom during World War II .